Question

In my Java test was the next question:

there is the next method:

public void changer(int[] x, int y) {

    x[y] = x[y] +3;
    y = y * 2;
}

We have array named a, with the values:

2,4,0,1,-6,3,8,7,5

if b = 3

what will be a and b values after the next call:

changer(a,b);

My answer was:
b = 6

a = 2,4,0,4,-6,3,8,7,5

I’ve tested it on BlueJ and got the same answer, but the tester wrote: wrong !

what do you say?

Answer 1

You are right about array values, but wrong about b value.

When you call a method, java passes everything by value, that mean that changing y only changes the value locally, and the change is not reflected on b.

However, when passing arrays and objects, a value representing a pointer to the array is passed. That means that x = new int[8] does not alter a at all, since as it happens for y the change is not reflected to a. However, changing array members or object properties works as you expected, cause a and x both point to the same array in memory.